hw/misc/pvpanic: centralize definition of supported events

hw/misc/pvpanic: centralize definition of supported events

The different components of pvpanic duplicate the list of supported
events. Move it to the shared header file to minimize changes when new
events are added.

MST: tweak: keep header included in pvpanic.c to avoid header
dependency, rebase.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
Message-Id: <20240527-pvpanic-shutdown-v8-3-5a28ec02558b@t-8ch.de>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>